1. Field of the Invention
This invention relates to a method for producing methanol from a carbon oxide selected from the group consisting of carbon monoxide and carbon dioxide and hydrogen gas. More particularly, this invention relates to a method for producing methanol which comprises reacting a gas containing (1) a carbon oxide selected from the group consisting of carbon monooxide and carbon dioxide and (2) hydrogen gas in the presence of a catalyst comprising palladium supported on at least one metal oxide selected from the group consisting of the metals of the Group IIa and Group IIIa of the short form of the Periodic Table.
2. Description of the Prior Art
A typical method for producing methanol from a synthetic gas which has conventionally been practiced on an industrial scale comprises reacting the synthetic gas under a pressure of 300 to 350 atms. at a temperature of 300.degree. to 400.degree. C. in the presence of a catalyst comprising zinc oxide and chromium oxide (ZnO-Cr.sub.2 O.sub.3), as disclosed in German Pat. Nos. 415,686 and 462,837. Also, a method for producing methanol as described above but using a catalyst where an appropriate amount of copper is added to the above catalyst (ZnO-Cr.sub.2 O.sub.3 -Cu) and using a pressure of 50 to 150 atms. and at a temperature of 250.degree. to 300.degree. C. has been known, as disclosed in Japanese Patent Publication No. 8266/55.
These conventional synthetic methods for producing methanol using a catalyst is effectivve to a certain degree but is still required to be improved in the process technique since the reaction of these methods should be operated at a high pressure and at a high temperature. In fact, the improved method for the synthesis of methanol using the Cu-containing catalyst as described above is considered to have been developed as a result of study on reducing pressure and temperature in the operation of methanol synthesis.
However, a multi-component catalyst containing Cu has a disadvantage in that it tends to be poisoned with sulfur or nitroge-containing compounds which are present even in a small amount in the synthetic gas as impurities whereby the life of catalyst is shortened. The synthetic gas which is presently available in industry from the naphtha origin generally has a gas pressure of 15 to 30 atms. and can be further pressurized to about 50 atms. by the rotatory compression method. The methanol synthesis using the synthetic gas of such low to middle pressure range as a raw material is expected to be an efficient industrial technology for the methanol synthesis in future.
Hitherto, palladium powder or palladium metal tips have not been considered to be an effective catalyst for the synthetic gas conversion since they are inactive to the CO--H.sub.2 reaction or they only function as slightly promoting the methane formation in the CO--H.sub.2 reaction, as described in F. Fischer, H. Tropsch, P. Dilthey, Brennstoff-Chem., 6, 265 (1925). For example, in the reaction of a mixed gas of CO and H.sub.2 under atmospheric pressure at a temperature in the range of 200.degree. to 300.degree. C. using a palladium catalyst prepared by supporting palladium on an alumina carrier, the production of methane and a small amount of hydrocarbons of C.sub.2 -C.sub.5 is promoted, but oxygen-containing compounds useful as industrial raw materials such as methanol and the like are not produced at all, as reported in M. A. Vannice, J. Catal, 37, 449 (1975) or only several percent of the consumed carbon monoxide is converted into methanol under reaction conditions using a mildly low pressure of 5 to 25 kg/cm.sup.2 and a high CO/H.sub.2 ratio, as reported in Belgian Pat. No. 849-121 (1977).